1. Field of the Invention
Embodiments of the present invention generally relate to substrate processing techniques. More specifically, the present invention relates to processing techniques for creating desired thermal profiles during substrate processing.
2. Description of the Related Art
Rapid thermal processing (RTP) and rapid thermal chemical vapor deposition (RTCVD) annealing processes, and the like (collectively and generically referred to herein as “conventional heating processes”), traditionally use a furnace with infrared radiation generated by halogen lamps to heat a substrate. The substrate, commonly made of silicon, is disposed in a controlled atmosphere enclosure, and the infrared radiation is directed onto the superficial face of the substrate through a transparent window.
The temperatures reached during thermal processing operations may be high, often over 1000° C., with thermal gradients liable to reach several 100° C./second or higher. One important parameter of such substrate processing is the uniformity of the temperature over the entire surface of the processed substrate. The presence of thermal gradients of just a few degrees between the various portions of the substrate can cause defects in the substrate. However, heat loss near the edges of the substrate is much greater than near the center, which leads to lower temperatures at the edge of the substrate.
Several solutions have been proposed to compensate for this temperature inequality. Some examples include: a metal reflector positioned at the rear of the lamps, heating both sides of the substrate with two sets of lamps arranged along opposite sides of the reactor, heating by zones in the reactor, the use of heated susceptors, and fitting an edge ring to minimize heat transfer through the sides of the substrate. However, despite any improvements these solutions may have provided, thermal gradients continue to exist sufficient to cause defects in the substrates.
Therefore, there is a need in the art for a method and apparatus that generates desired substrate thermal profiles when subjected to these heating processes.